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  • #41080
    Jim Jennings
    Participant

    Just finished a new model. We are calling it the “Mustang”. It has a 64″ wing that occupies 463 sq.in. of area. N9 Airfoil. The stab is 122 sq. in. RTF weight is 455g. It has a Axi 2212 on the nose. With the battery located on the CG it can be flown with a variety of different power configurations. It currently has a 1200mah 2 cell with a 10 X 8 prop Starlink timer, and a servo DT.



    #47091
    George Reinhart
    Participant

    WOW!!!
    Way to go.
    Cheers!

    #47092
    rivers
    Participant

    Nice plane Jim, it looks like a winner.

    I see you’re going back to the concept of low voltage (2 cells), high current, with a relatively large prop. This goes back to Chuck’s teachings which assert that a large prop is more efficient and can produce more propulsion for a given input power. We know this is true from theory. However, we also know that small props spinning at high speeds can be successful. It seems that the small props, although not very efficient, produce aerodynamic conditions that make an uncontrolled free flight model easier to trim.

    I have models of both types, and I’m going to devote time this year to try to understand the pros and cons of both types.

    Dick

    #47093
    GRAHAM WEBSTER
    Participant

    Jim,
    Model looks good, simple question what is it coverd with and why the choice?
    I am new to electric and in the middle a two new models, which prompted the question.
    Have a great season.

    #47094
    Jim Jennings
    Participant

    Graham, I like to use Microlite. It is made by Coverite and marketed for park fliers. It has several good properities, very lite, easy to use, comes in transparent colors for visibility and is impervious to weather conditions.

    Dick, Although I am a student of Mr. Groth, on contest day I will be spinning a smaller prop faster. A few initial flights on low voltage is also from the teachings of Mr. Groth. I do not believe the answer is small or large. I belive optimum is somewhere in the middle. I am still looking for optimum. I am encouraged with this model. Particulary with the improved wing loading over last years model.

    #47095
    DAN BERRY
    Participant

    Jim, that’s a pretty airplane.
    Is the wing-loading less than what you had at NATS last year?
    All-up weight seems to be higher. Is this the same motor pkg as the 404 Maverick?

    #47096
    Jim Jennings
    Participant

    It has 59 sq. in more wing than last year’s model. Power is yet to be determined. Last year’s model had a 2208 and a 700mah 3 cell. Both of those componets are lighter than the 2212 and the 1200mah 2 cell currently on this one. The answer to your question is , it depends on the power. I plan to build at least 2 more to get the bugs out of the kit, get a lighter model and look at different power packages. I may try a Little Screamer on the next one.

    #47097
    Anonymous
    Inactive

    Jim-

    Which of the 2212 versions are you using in the “Mustang”?

    Regards,

    Larry

    #47098
    Jim Jennings
    Participant

    It is an Axi 2212/12, 1950kv.

    #47099
    ARAM SCHLOSBERG
    Participant

    Jim,
    A beautiful model! As a curiosity, what 2S battery are you using?

    The motor choice is interesting. The AXI 2212/12 with a Kv 1950 will run a 8×4” prop with a model weighing 800 grams (according to Pacific Models http://www.rcmodels.ca), weighing 57 garms with leads. The next motor, which I am using, is the AXI 2217/12 with a Kv 1380 with a 11×4” prop weighing 69.5 grams.

    A motor’s selection boils down to a choice of more power (using larger and slower 11-12″ props) coupled with more torque versus less power (7-8″ props) and less torque. The advantage of the smaller prop approach closely mimics conventional piston motors (high RPM and small props) and is a perfect fit to the standard power models, explaining its popularity.

    The large prop approach requires dealing with high torque and the wider slip stream disk behind the prop. Auto surfaces might prove be helpful and looking at the way T-birds and other shoulder trust models are trimmed gives useful insights. Chuck Groth was able to solve this problem by using extraordinarily high pylons – keeping the wing out of the slip stream. But it was at the NiCad age.

    A median prop size approach might result with the worst traits of both schools of thought.

    #47100
    GRAHAM WEBSTER
    Participant

    Hi Jim,
    Tks for the note on the new model. I assume ( some time not the best of things to do) that this is for F1Q or “B” or both!!
    Once you have a kit ready let me know, who know one day I can loose electics like I used to loose power models. Is that why RC was invented, never thought of that before!!1

    #47101
    Jim Jennings
    Participant

    Graham, This models destiny has not been determined. I will build a few and see which flies the best. It will be available in kit form. Try radio DT.

    Aram, it is a Enerland. I am not a fan of big props. You might want to consider a 9 X 6″ prop and a 3 cell on the 2217/12.
    http://www.modelmotors.cz./index.php?page=61&product=2217&serie=12&line=GOLD

    #47102
    GRAHAM WEBSTER
    Participant

    Hi Jim,
    I finished the model, or at least some part of it!!!! All up weight is 454 gms!! Close. I am making two versions, I like your fuselarge better than mine, never could get the thing square !!!One version uses only the fuselarge from the kit, rest is my design based on a SLOP model. The second version will basically be the std kit with a slight change to fuselarge and wing. With so many option on motors, ESC, Timers , batteries I need to have as many hatch’s as possible to change/adjust the bits and pieces.
    Motor is 2212/6 ( 2200 KH) knock off up front, std 20 ESC, Z-tron timer and a Tenergy 25C 2200mAH 7.4 2 cell battery. This may be underpowered but it is a place to start.
    If suitable encouragement is forth coming I may post pics, I need help on how to load the pics, all my current attempt failed ,HELP!!
    What everone else up to!!!!
    Happy week-end y’all!!!!

    #47103
    GRAHAM WEBSTER
    Participant

    Jim,
    My mistake, the battery I quoted is above the limit ( it weights 124 gms!!). So I need to find an alternative , any suggestions? Is the debate 2 or 3 cells ?
    On the same subject of batteries has anyone run tests to compare different manufactures?
    As always any help is appreciated.

    #47104
    Jim Jennings
    Participant

    Graham, Dick Ivers has done more research and testing on Lipos than anyone that I know. He could give you a more informed opinion. I have settled on a power system that I like alot and plan to stick with. The Axi 2212/12, a 7 X 5 prop, 30 amp Jeti, and a Enerland 3 cell 800 mah 30c lipo. It delivers all of the power I want in a light weight package. There is a big difference in the quality of the lipo cells on the market today. Enerland makes a quality pack with a discharge rate that works for us. Let us know how it turns out.

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